"He looked at me strangely and pushed and snorted my right breast and pushed and snorted?And I'm thinking, something's not right," said Witcher.

Whether the dog really knew it or not, it turns out Carol had breast cancer. It's thought a dog's keen sense of smell can sniff out cancer. But it was a breath test that doctors say confirmed it.

Doctors have known since the Middle Ages that the aroma of breath can be a clue to what's wrong with a patient. For example, a sweet smell may signal uncontrolled diabetes. A fishy odor is associated with advanced liver disease. A urine-like smell may come when kidneys are failing.

This experimental test measures organic compounds expelled from the lungs, and identifies the ones linked to breast cancer.

"What this does is you just breathe into it and we measure just from the breath," said Charlene Bayer, Ph.D., GA Tech Research Institute.

A pilot study shows the test was 77-percent accurate in distinguishing cancer. For mammograms, the success rate is 80-percent.

"Very exciting to potentially put this in the primary care physicians office as, again, a direct read system where a patient could be told right away yes it looks like something's there, go an get your mammogram earlier," said Dr. Sheryl Gabram, Emory University, Winship Cancer Institute.

These biomarkers can also show up in salvia, blood, urine hair and more.

The quest to come up with an inexpensive, easy to use and accurate test is ongoing in labs across the country.

"Our accuracy rate right now is in the mid 90s," said biochemist Jeffry Borgia, Ph.D., Rush University Medical Center.

Dr. Borgia is working on a pin prick blood test that would also give patients the heads up that something may or may not be going on in their lungs. The decision could then be made to determine whether a more involved screening is needed.

"All you really need to say is there's a cancer, go have another test done. And that's the idea of a cheap screening test?is that there is a problem, go see somebody and have another test done," he said.

Borgia says the future of biomarker tests will depend on whether they can look for multiple problems all at once. And for patients at high risk, the greatest appeal may be the ability to do screenings more than once a year.

"Maybe even multiple times a year, kinda look to see what is going on in terms of do you have cancer or not," said Borgia.

With early detection and treatment, Carol Witcher is now cancer free.

The breath test is still experimental and researchers say it will likely never replace the mammogram.